Had the same problem with Raspi 4B.
Problem was dependent on screen resolution (!!).
With 1920x1080, wlan0 became disconnected after it was
ok at lower screen resolutions. Was in 2.4GHz band.
After turning on 5GHz in the router and going into
the network preferences (right click the network icon top
right on screen) and SSID ... and checking "automatically
configure options" the connection remains stable (so far :D ).
